Misoprostol (brand name: Cytotec) is a prostaglandin product which can be applied to the cervix to induce labour. It is also known as Prostaglandin E1, but is not the same as the more common Prostaglandin E2 gel, dinoprostone. Misoprostol is cheaper than Prostaglandin E2, and apparently the induction to delivery interval is reduced, but uterine hyperstimulation appears more likely. This is particularly dangerous with VBAC candidates as the risk of uterine rupture is increased, compared with spontaneous labour, and also with induction by prostaglandin E2 gel and by oxytocin.
Marsden Wagner, retired from the World Health Organisation, has called for misoprostol induction on mothers attempting VBAC to stop, on the basis of the current evidence. You can read his views in the British Medical Journal.
A magazine article about this drug and its dangers for women attempting VBAC is on Salon.com:
Cytotec: Dangerous Experiment or Panacea? by Ina May Gaskin.
Here are summaries of some studies on misoprostol and VBAC attempts:
Obstet Gynecol 1998 May;91(5 Pt 2):828-30
Wing DA, Lovett K, Paul RH
Department of Obstetrics-Gynecology, University of Southern California School of Medicine, Los Angeles, USA
Researchers planned to compare misoprostol to oxytocin for induction of labour in mothers attempting a VBAC. After two uterine ruptures among just seventeen mothers receiving misoprostol, the trial was stopped on safety grounds. They concluded: "When misoprostol is used in women with previous cesareans, there is a high frequency of disruption of prior uterine incisions."
This study compares Misoprostol with Prostaglandin E2 gel:
Am J Obstet Gynecol 1999 Jun;180(6 Pt 1):1551-9
Blanchette HA, Nayak S, Erasmus S
MetroWest Medical Center, Department of Obstetrics and Gynecology, British Columbia, Canada.
Eighty-one mothers whose labour was induced with prostaglandin E2, were compared with one hundred and forty-five who were induced with misoprostol (prostaglandin E1).
The mean time between induction and birth was approximately a third shorter with misoprostol: 19.8 hours compared to 31.3 with prostaglandin E2. There was no significant difference in the cesarean delivery rate with misoprostol (25.6% vs 22.2%). There were no uterine ruptures among the 81 women induced with prostaglandin E2. However, among the 145 induced with misoprostol, there were 2 uterine ruptures and 1 dehiscence among mothers attempting VBACs, and 1 rupture in a mother with no prior caesarean. One baby died as a result of uterine rupture after misoprostol induction, but otherwise outcomes for the babies were similar.
CONCLUSIONS: "Compared with prostaglandin E2, misoprostol is more effective in cervical ripening and induction of labor, is as safe for patients who do not have a history of cesarean birth, may carry a higher incidence of uterine rupture, and should not be used for patients attempting vaginal birth after previous cesarean delivery"
It is surprising that the researchers considered misoprostol to be as safe as Prostaglandin E2 gel for mothers who did not have a history of caesarean births, since one woman in their study had a ruptured uterus in these circumstances. Uterine ruptures are very rare in mothers with unscarred wombs, so this result should raise questions rather than reassure.
Am J Obstet Gynecol 1999 Jun;180(6 Pt 1):1535-42
Plaut MM, Schwartz ML, Lubarsky S
Department of Obstetrics, Northwest Permanente PC, British Columbia, Canada.
Out of 89 women attempting VBAC whose labours were induced with misoprostol, 5 suffered uterine ruptures. However, among 423 women attempting VBAC who did not receive misoprostol, only one suffered a rupture. The rupture rate for VBAC candidates after misoprostol induction was therefore 5.6%, compared to 0.2% otherwise.
CONCLUSION: Misoprostol may increase the risk of uterine rupture in the patient with a scarred uterus. Carefully controlled studies of the risks and benefits of misoprostol are necessary before its widespread use in this setting.
Aust N Z J Obstet Gynaecol 1998 Feb;38(1):96-7
Sciscione AC; Nguyen L; Manley JS; Shlossman PA; Colmorgen GH
Department of Obstetrics and Gynecology, Medical Center of Delaware, Newark, USA.
A single case study where a mother with a previous low transverse Caesarean delivery suffered a uterine rupture after transvaginal misoprostol was used.
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